Thanks again to all for the advice upthread. I booked my tickets yesterday; I am arriving into MAD at 0800 on a Sunday on a DL flight and then need to take an AVE or Iryo train to Zaragoza where I will spend the night at a hotel that I suspect will be in the Old Town/Centro area.

My questions are as follows:

I know that I will need to allocate time to clear customs and immigration at MAD and then make my way over to T4(S) to take public transit to Atocha. I'm thinking to give myself four hours for this; does this sound about right or could I safely make it in three hours?

If I get a Combinado Cercanias ticket, would that cover the legs between Barajas and Atocha in Madrid *and* Delicias and Centro in Zaragoza? If so, this seems a no-brainer as the best/cheapest option unless I am missing something.

Thanks in advance!